Potassium

The major intracellular ion

Potassium (K), a cation, is the most abundant cation in the body cells. Ninety-seven percent of the body’s potassium is found in the intracellular fluid (ICF) and 2-3% is found in the extracellular fluid (ECF), Which comprises of intravascular (in vessels) and interstitial fluids (between tissues). Potassium is also plentiful in the gastrointestinal tract. It is the 2-3% in the ECF that is all important in neuromuscular function. Potassium is constantly moving in and out of cells according to the body’s needs, under the influence of the sodium-potassium pump.

The normal serum potassium concentration ranges from 3.5 mEq to 5.5 mEq/liter; even minor variations are significant. The normal plasma/serum potassium range is narrow; therefore, a serum potassium level outside the normal range may be life threatening. A serum potassium level less than 2.5 mEq/L or greater than 7.0 mEq/L can cause cardiac arrest. Thus, serum potassium values need to be closely monitored.

Normal renal function is necessary for maintenance of potassium balance since 80% of the potassium excreted daily from the body is by way of the kidneys. The other 20% is lost through the bowel and sweat glands.

Potassium must be replaced daily; approximately 40 mEq to 60 mEq/day suffice in the adult if there are no abnormal losses occurring. Dietary intake in the average adult is 50 mEq to 100 mEq/day.

Potassium influences both skeletal and cardiac muscle activity. For example, alterations in its concentration change myocardial irritability and rhythm. Alterations in acid-base balance have a significant effect on potassium distribution. The mechanism involves shifts of (K+) between the cells and extracellular fluid. Hypokalemia can cause alkalosis and, vice versa, alkalosis can cause hypokalemia. For example hydrogen ions move out of the cells in alkalotic states to help correct the high pH and potassium ions move in (to maintain electroneutrality). Hyperkalemia can cause acidosis and vice versa, acidosis can cause hyperkalemia. For example, in acidotic states, some of the excess hydrogen ions enter the cells to help correct plasma pH. In so doing, potassium ions are released from the cells in order to maintain electroneutrality.

Knowledge of the above facts helps in the detection of abnormal potassium state when pH disturbances are present. In such situations it is possible that the serum potassium levels will appear normal even when total body deficits or excesses are present.

FOODS RICH IN POTASSIUM

Cereals

Fruits

Beans

Vegetables

Beverages & Other

Kellog’s All Bran 532

Dried Apricots 454

Pinto Beans 531

Baked Potato
593

Orange Juice
479

Nabisco 100% Bran 354

Cantaloupe 412

Kidney Beans 452

Baked Winter Squash 590

Grapefruit Juice
360

Bran Flakes
251

Prunes
353

Lentils
374

Baked Sweet Potato 528

Tomato Juice
552

Shredded Wheat 155

Banana
338

Black Beans 309

Spinach
440

Tomato Sauce
459

Raisins
225 (3tbs)

Avocado
510

Canned Beans 332

Peas
296

Blackstrap Molasses 1218 (2tbs)

Trivia

Did you know… That the food highest in Potassium is not bananas. Actually it is Avocado which has 38.1 mEq of potassium compared to a banana which has 11.6 mEq of potassium. Other good choices are Baked Potato 12.9 mEq, Raisins 19.3 mEq, Canaloupe 12.7 mEq, Dates 13.9 mEq, and Orange Juice with 11.2 mEq.